This invention relates generally to filter-driers for refrigeration systems and particularly to a casing and a molded filter-drier core having superior structural characteristics of attrition resistance, strength and permeability while being held firmly in place by structural cooperation between the casing and the core.
Filter-driers are used in refrigeration systems to filter solid contaminants and to remove soluble contaminants from the refrigerant and lubricant. The three general types of construction of filter-driers are loose fill, compacted bead, and molded core.
In a loose fill design, the desiccant is captured within mesh screens to prevent the desiccant beads from escaping into the system. The beads form a desiccant bed trapped between the shell and mesh screens, however, within the desiccant bed the beads are only loosely held. Flow of refrigerant through the desiccant bed or vibration of the filter-drier shell from other sources results in undesirable movement of the individual beads within the bed. Contact of the desiccant beads with the shell, mesh screens, or other desiccant beads can lead to attrition of the desiccant beads. As attrition of the beads progresses, the desiccant fines escape the mesh screens and circulate in the refrigerating system.
Compacted bead designs use desiccant beads similar to the loose fill design but incorporates perforated metal and mesh screens, filter pads, and springs to compact the desiccant bed. The compaction of the desiccant bed restricts the movement of the individual beads compared to a loose fill design and reduces the risk of attrition, however, this design does not eliminate attrition.
A molded core unit consists of a molded desiccant block held in place with support screens, filter pads, and springs. The molded core is made of smaller granules of desiccant than the loose fill or compacted bead design. The desiccant granules are bonded together using an organic or inorganic binder to form a solid shape. This design prevents attrition of the desiccants by not allowing movement of the granules.
Typically, shells to contain the desiccants in a filter-drier are either welded steel shell consisting of steel tubing and/or stamped pieces welded together to form a sealed shell. Alternatively, copper spun shells may be used in which copper tubing is reduced to a specific fitting size. Prior to welding a steel shell or spinning to reduce the diameter of the copper tubing, the internal parts consisting components such as perforated screens, mesh screens, filter pads, desiccant, and springs are assembled. The purpose of the screens and springs is to contain the desiccant beads or desiccant core.
Known filter-drier units having molded cores and incorporated herein by reference, are disclosed in U.S. Pat. No. 2,556,292, U.S. Pat. No. 5,440,898, U.S. Pat. No. 5,562,427 and U.S. Pat. No. 2,551,426. U.S. Pat. No. 2,556,892 discloses a core formed from molded discs and U.S. Pat. No. 5,440,898 disclosed a molded core which is strengthened by the use of fibers. In both cases, the core is spaced from an outer metal casing and held in place by a lateral support system at each end. U.S. Pat. No. 5,562,427 discloses a copper casing with longitudinally spaced grooves formed to hold a preformed solid core. The grooves are formed by the drawing process but are at each end of the core. U.S. Pat. No. 2,551,426 discloses a preformed block of drying agent which is supported by longitudinally spaced internal protrusions.
The present system overcomes the need for support systems for holding the core in place in a manner not disclosed in the known prior art.
This molded core filter drier does not require additional parts to hold the core in place within the casing and the core is formed within the casing and held within the casing by structural cooperation between the casing and the core. The binder used in the molded core serves to bind the desiccants together and, in addition, binds the desiccant core to the casing. Thus movement between the core and the casing is prevented thereby substantially eliminating desiccant attrition. It is an advantage to provide a filter bonded to the core.
This filter-drier is for drying refrigerant circulated in a refrigeration system by removing moisture therefrom, and comprises a casing having an inlet for receiving refrigerant, and an outlet for discharging refrigerant. The casing includes opposed end portions and an intermediate portion disposed between said end portions. A molded core is provided including inlet and outlet end portions having a through passage therebetween disposed in said casing between said inlet and outlet and receiving flow of refrigerant therethrough and holding means is provided between the casing and said core for holding the core in place within the casing and a filter is bonded to the core, as by molding.
It is an aspect of this invention to provide that the filter is bonded to both of said molded core end portions.
It is another aspect of this invention to provide that the core passage has opposed open ends and is lined with a filter.
It is still another aspect of this invention to provide that the core passage is generally cylindrical.
It is yet another aspect of this invention to provide that the core passage open ends include annular portions, and the filter is bonded to said annular portions.
It is an aspect of this invention to provide a casing having an inlet for receiving refrigerant and an outlet for discharging refrigerant, and opposed end plates each having inlet and outlet openings having check valves defining the direction of the flow. A molded core is provided including inlet and outlet end portions having a through passage therebetween said core being disposed in said casing and held in place between said opposed end plates and receiving flow of refrigerant therethrough, said core including opposed inlet and outlet end faces and said passage being cylindrical. A filter media is provided including a cylindrical portion lining said passage and annular end portions, said filter media being molded to said core.
It is another aspect of this invention to provide that each end plate includes two openings; one of said openings being aligned with the passage and the other of said openings being offset from the passage.
It is an still another aspect of this invention to provide that the inlet opening is offset and the outlet opening is axially aligned.
It is another aspect of this invention to provide a method of manufacturing a filter-drier desiccant core for a heat pump filter-drier having a tubular casing and a two-way valve system to provide two-way flow through the core between an inlet and an outlet comprising the steps of providing a tubular mold to form the outer diameter of the mold; providing a center post within the tubular mold to form the inner diameter of the core; providing a mold base associated with the tubular mold at one end of the core; placing a filter media over the mold base and the center post; depositing a desiccant/binder within the mold and over the filter media; and placing a filter media over the desiccant/binder at the other end of the core to bond the filter media to the core and removing the mold when the core has set.
It is another aspect of this invention to compress the desiccant/binder to ensure a good bond with the filter media and another aspect to provide that the filter media is molded to the core.
This filter-drier is relatively inexpensive and simple to manufacture and is particularly effective for its intended purpose.